1. Field of the Present Invention
The present invention relates to a positioning method and system, and more particularly to an interruption flee navigator for both stationary and hand-held applications, which can ensure the user be provided with accurate positioning data continuously anytime and anywhere, no matter the user is located inside a building, tunnel, forested area, unbanized terrain, or high jamming environment where GPS signals are normally not available.
2. Description of Related Arts
Current hand-held navigator depend on the GPS (Global Positioning System). The GPS is a satellite radio-navigation system, which is owned, deployed, and operated by the U.S. Department of Defense, but is available for commercial uses around the world. Unfortunately, GPS is vulnerable to jamming and shadowing, especially in hand-held application on hand, so that a GPS receiver often can not provide continuous positioning information without interruption, especially in urban area. For commercial hand-held applications, it is very important to obtain continuous positioning information in urban area. On-the-fly ambiguity resolution is one the most recent addition to the GPS to toolbox to determine the correct number of initial integer cycles in carrier-phase measurements, while a receiver is in motion, as indicated, in another patent application of the applicant application Ser. No. 09/611,568.
Traditionally, an inertial navigation system (INS) is an interruption-free navigation system, which does not need to receive any external radio frequency signals to Output position data continuously. However, the cost, size, power, and position-drift characteristics of conventional inertial navigation systems prohibit them from use in commercial hand-held navigation applications.
Therefore, it is very desirable to develop a navigator with reasonable size and weight and power consumption for hand-held operation without interruption, which can be used in the areas where GPS signals are not available, such as inside buildings, tunnels, forested areas, urbanized terrain, and high jamming environments.
Moreover, it is well known that the position errors of an inertial navigation system drift with time and GPS has a poor accuracy of vertical positioning. The long term accuracy of GPS and inertial navigation system integration solution mainly depends on the performance of GPS. It means that the GPS and inertial integrated navigation system can not improve the vertical positioning performance. For some applications, such as commercial and military operations inside a skyscraper, altitude accuracy and environment situation data are very critical.
The main objective of the present invention is to provide an interruption free navigator to determine position information of a user with high accuracy, wherein the present invention can ensure the user be provided with accurate positioning data continuously anytime and anywhere, no matter the user is located inside a building, tunnel, forested area, urbanized terrain, or high jamming environment where GPS signals are normally not available. In order to accomplish the main objective, the interruption free navigator comprises a main IMU based interruption-free positioning module for sensing motion measurements of the user and produce interruption-free positioning data of the user, a positioning assistant which is incorporated to provide interrupted or continuous positioning data to assist the main IMU based interruption-free positioning module to achieve an improved interruption-free positioning data of the user, a wireless communication device which is built in to exchange the user position information with other users, and a display device which is attached to provide location and surrounding information by selectively accessing a map database with the user position information
Another objective of the interruption free navigator of the present invention is to determine position information of a user with high accuracy. The system of the present invention can receive but not rely on GPS signals and DGPS (differential GPS) signals for a highly accurate positioning solution. Without GPS/DGPS signals, the system also provides a highly accurate positioning solution, such as an accuracy of better than 1 percent of the distance traveled. The system is a right positioning system with reasonable size and weight and power consumption for commercial stationary or hand-held operation, which can be used in areas where GPS signals are not available, such as tunnels, forested areas, urbanized terrain, and high jamming environments.
Another objective of the interruption free navigator of the present invention is to determine position information of a user with high accuracy, wherein an altitude measurement device and/or an object detection system are incorporated to further meet other needs such as improving the vertical positioning performance.
Another objective of the interruption free navigator of the present invention is to determine position information of a user on land with high accuracy, such as an accuracy of better than 1 percent of the distance traveled without relying on GPS, wherein output signals of an inertial measurement unit, a velocity producer, and a north finder are processed to obtain highly accurate position measurements of the user on land.
Another objective of the interruption free navigator of the present invention is to determine position information of a user with high accuracy, wherein a wireless communication device is built in to exchange the user position information with other users.
Another objective of the interruption free navigator of the present invention is to determine position information of a user, wherein a display device is employed to provide location and surrounding information by selectively accessing a map database with the user position information.
Another objective of the interruption free navigator of the present invention is to fuse information from the IMU, a velocity producer, and a north finder to achieve a highly accurate interruption-free navigation solution with hardware and software modules, including the following capabilities:
(a) Interruption-free navigation.
(b) Autonomous position error xe2x89xa61% of the distance traveled when GPS RF (radio frequency) signals are not available.
(c) Low cost, low power consumption, lightweight.
(d) A unique sophisticated Kalman filter. It removes the inherent drift of the free inertial positioning solution derived from the output of the low cost xe2x80x9ccore microxe2x80x9d IMU by means of fusing information from the xe2x80x9ccore microxe2x80x9d IMU, magnetic heading sensor, and velocity producer.
(e) Smoothing of the output noise of the magnetic sensor and velocity producer.
(f) Innovative state variable selection and measurement design of the Kalman filter,
including position update, relative position update, heading update, and automated zero velocity update.
(g) Autonomous multiple user stop tests and associated zero-velocity updates. The user stop is not required to perform a zero-velocity update. But, if the user stops at will, the system can exploit such a benefit autonomously.
(h) Advanced IMUxe2x80x94MEMS (MicroElectroMechanicalSystems) and ASIC (Application Specific Integrated Circuit) based xe2x80x9ccore microxe2x80x9d IMU: Miniaturized (Length/Width/Height) and Lightweight; High Performance and Low Cost; Low Power Dissipation; Exceptional Improvement in Reliability.
(i) Map database and software module to access surrounding information using the current position solution.
(j) Display device and software module to visualize the location of the user and the surrounding information.